This invention relates generally to machines used to apply various types of liquid adhesives to sheet materials such as paper, cloth, leather, cardboard, plastic, etc. The invention is particularly directed to improvements in such machines for facilitating access to and the cleaning of the various components of the machine which may become clogged with adhesive during operation.
Adhesive applying machines of the kind to which this invention relates, generally include a tank or reservoir to hold the adhesive, a coating roller, a system of transfer rollers for supplying a uniform coating of adhesive to the coating roller from the tank or reservoir, one or more feed rollers for feeding the sheet material into tangential contact with the coating roller whereby the adhesive is transferred to the sheet material, and stripping elements for stripping the adhesive coated sheet material from the surface of the coating roller to ensure that the sheet material will not stick to the surface of the coating roller and will be delivered to a conveyor belt or other means for transporting the coated sheet material away from the adhesive applying apparatus. During operation, sheet material to be coated with adhesive is fed into the machine where it is passed through a gap between at least one feed roller and the coating roller so as to transfer the adhesive to the side of the sheet material in contact with the coating roller.
In adhesive applying machines of this type, it is necessary, from time to time, to clean the feed rollers, the coating roller and the stripping elements in order to remove excess adhesive, pieces of sheet material or other foreign matter with which the machine becomes clogged. In the usual operating configuration, the feed rollers are located generally below the coating roller and the stripping elements are located generally behind the coating roller. In these positions they are inaccessible for cleaning purposes, so that a practical machine of the described character must have some means for affording ready access to the feed rollers and stripping elements.
In some designs of this type of machine, the coating roller is displaced to provide access to the feed rollers and stripping elements. However, due to the great weight of the coating roller this method has been generally found to be unsatisfactory. The mechanism for displacing the coating roller must have a great mechanical advantage, and consequently takes a great amount of time to operate.
Furthermore, for proper machine operation, the distance between the coating roller and the transfer roller which transfers adhesive to the coating roller must remain constant over the life of the machine. If the coating roller is displaced during cleaning, it is often difficult to return it to its proper location relative to the transfer roller, and as the cleaning mechanism for displacing the coating roller wears over time, the proper relationship between the transfer roller and the coating roller is often disturbed.
More recent designs such as that shown in U.S. Pat. No. 3,000,347 move the feed rollers and the stripping elements away from the coating roller to provide access for cleaning rather than move the coating roller. While this has the advantage of maintaining the proper relationship between the coating roller and the transfer roller, it has the disadvantage of disturbing the relationship between the coating roller and the feed rollers.
Furthermore, the design shown in U.S. Pat. No. 3,000,347 requires a complicated gearing arrangement to drive the feed rollers in the cleaning position as well as in the operating position. This provides a definite advantage during the cleaning operation. The present invention utilizes a much simpler gearing arrangement to achieve this desirable end result.
During operation, the stripping elements in this type of machine are in contact with the coating roller at a point downstream of the point where the sheet material contacts the coating roller. Regardless of design, this contact causes the stripping elements to accumulate adhesive. To avoid the accumulation of an excess amount of adhesive, it is well known that the contact portion of the stripping element in contact with the coating roller should be the lowest point on the stripping element. Thus, as the stripping element strips off adhesive, the adhesive tends to drip back to the contact point where it is carried away by the coating roller.
Previous designs have not maintained this relationship (i.e., maintained the contact portion of the stripping element below the remainder of the stripping element) as the stripping elements are moved into the cleaning position. Thus, in previous designs, as the stripping elements are moved into the cleaning position, adhesive on the contact end of the stripping elements has dripped back down the stripping elements contaminating the previously uncontaminated portions of the stripping elements just prior to the time when the cleaning operation begins. The present invention eliminates this problem by maintaining the contact portion of the contact end below the remaining portion of the contact end as the cleaning rollers and stripping elements are rotated into the cleaning position.
Additionally, the present invention allows the stripping elements to be easily removed for cleaning.